The £8m contract will also see PB draw up the construction programme to re-establish a passenger and freight rail link between Oxford and Bedford, Milton Keynes and Aylesbury for the first time in more than 40 years.
It involves upgrading and reconstructing underused and disused sections of railway.
Work to electrify the line between Oxford and Bletchley will undertaken at the same time.
Phase 2
EWR works east of Bicester to Bletchley and Bedford, including the Aylesbury to Claydon Junction line within this five-year period ending March 2019.
Work involves upgrading the Bicester Town to Bletchley and Claydon Junction to Aylesbury freight line for passenger services
Building a new station at Winslow
Building new high level platforms at Bletchley Station and minor upgrades to the existing Bletchley to Bedford passenger railway.
Andy Milne, Network Rail senior programme manager, said: “This contract award marks a significant milestone for the East West Rail scheme.
“The work Parsons Brinckerhoff will be carrying out will enable the project to be developed to the point where we can then award contracts for detailed design and construction.”
Carillion and Buckingham Group are working under an £87m contract to deliver the first phase of the scheme which involves doubling of track for more than 18km of railway to increase line speeds to 100mph along with a variety of other works.
This includes construction of new overbridges, underbridges and footbridges, along with closure of 37 level crossings.
A new station will be built at Oxford Parkway along with work to upgrade Bicester Town and Islip stations along with a new signalling system.